As is known in the art, a vehicle such as automotive vehicle is provided with a brake apparatus corresponding to each wheel. A disc brake widely adapted as a brake apparatus has: a rotor (disc) which rotates with the wheel: paired pads (friction materials) arranged so as to oppose each other across the rotor; a claw portion which presses one pad toward the rotor; and a piston which presses the other pad toward the rotor. With brake pedal operation by a driver, a brake fluid is supplied to a caliper to cause the piston to move toward the rotor, and the paired pads are each pressed so as to sandwich the rotor to generate a braking force.
Meanwhile, with the advance of automobile technology, in place of development of mechanical brake apparatuses which is operated by a liquid pressure of the brake fluid as described above, development of electrically-operated brake apparatuses including an actuator controlled by an electrical signal has proceeded. Since this brake apparatus is designed without a master cylinder, liquid-pressure piping, booster, etc., the size and weight of the apparatus as a whole can be reduced. Also, a braking force can be controlled with high accuracy. Therefore, for example, this brake apparatus can be easily applied to, for example, a vehicle having an automatic tracking function of automatically controlling an acceleration or braking force in accordance with the behavior of another vehicle travelling forward. Furthermore, development of electrically-operated parking brake apparatuses has proceeded. This apparatus has also a function of a foot brake apparatus capable of obtaining a braking force by brake pedal operation by a driver as a brake apparatus.
This electrically-operated brake apparatus is described in, for example, Japanese Unexamined Patent Application Publication No. 2014-062639. The brake apparatus described in this Japanese Unexamined Patent Application Publication No. 2014-062639 is an electrically-operated parking brake apparatus having a mounting (mounting bracket) fixed to a vehicle body and a caliper body (caliper) movably provided to the mounting via paired slide pin bolts.
The caliper body has a U-shaped section extending across a disc rotor, and is movable to an axial direction of the disc rotor. The caliper body includes a claw portion which presses one pad, and has a piston which presses the other pad. The piston is driven by a driving apparatus (actuator) which is operated by, for example, operation of a parking brake switch provided inside the vehicle or the like.
The driving apparatus includes a gear body (case) attached to a bottom of a cylinder portion and formed into a substantially “L” shape, and the piston is movably accommodated in the gear body. An electric motor and a speed reduction apparatus for reducing the rotation of the electric motor to increase torque are accommodated in the gear body. With this, while a small-sized electric motor can be adopted and provided to the driving apparatus, the electric motor can be arranged in parallel with the cylinder portion, thereby improving mountability on the vehicle.